This invention relates to a method and apparatus for controlling the temperature of cooling air that is used to cool molten glass contacting elements of a glass forming machine. More particularly, this invention relates to a method and apparatus for controlling the temperature of air that is used to cool molds in a glass container forming machine of the individual section (I.S.) type.
Commonly assigned U.S. Pat. No. 5,900,035 (Hoening, et al.), the disclosure of which is incorporated by reference herein, describes the cooling of an annular, split mold of a glass manufacturing machine by causing cooling air to flow around the mold, while the mold is closed and an article is being formed therein from glass at a sufficiently high temperature to be moldable. U.S. Pat. No. 3,586,491 (Mennitt), the disclosure of which is also incorporated by reference herein, and which was assigned to a predecessor of the assignee of the present invention, also discloses a glass manufacturing mold air cooling arrangement. Each of the ""035 and ""491 patents specifically describes the manufacture of hollow glass articles, such as food and beverage packaging containers, by a glass forming machine of the I.S. type, now the most widely used glass container forming machine type.
The cooling effect of an air stream used to cool a glass manufacturing mold, for an air stream of a given flow rate, is a function of the temperature of the air entering the cooling system. Thus, when ambient air is used, unless the temperature of the cooling air is controlled by heating and/or cooling it to maintain a constant temperature, the cooling effect of the air stream will vary, and this can lead to undesired variations in the properties of the glass articles being molded in the air-cooled mold and/or undesired variations in glass manufacturing cycle times to accommodate variations in mold cooling effects as a result of variations in mold cooling air temperatures.
To overcome glass forming mold cooling air temperature variations, it has been known to increase cooling air temperatures by mixing hotter air from a portion of the glass manufacturing plant, for example, from around a glass melting furnace, with a cooling air supply from an outside location. It has also been known to reduce cooling air temperature by injecting a water spray into a cooling air supply to cool the air supply by evaporation of the water spray. Of course, this latter technique is only capable of cooling the air supply until its moisture saturation level is reached, and can result in contamination of the cooling air stream unless the injected water is properly filtered before injection. It is toward a solution of problems associated with prior glass manufacturing mold cooling air temperature control systems that the present invention is directed.
According to an embodiment of the present invention, mold cooling air for a glass molding machine is heated to maintain it at a desired temperature for introduction into a glass molding machine by an indirect heat exchanger that is positioned upstream of the inlet to the cooling air blower. In this embodiment, the cooling medium is water and the water is obtained from a water cooling tower of a type that is usually present in a glass manufacturing plant. The water can either be obtained from the inlet to the water cooling tower, where it will be approximately 100xc2x0 F., or from the outlet from the water cooling tower, where it will be approximately 85xc2x0 F., or, when needed, the water from the water cooling tower inlet is mixed with water from the water cooling tower outlet, in which case a mixing valve is provided to mix water cooling tower inlet water and water cooling tower outlet water in proper proportions to ensure that the water temperature going to the heat exchanger will properly heat the cooling air supply going to the heat exchanger to maintain a substantially constant cooling air outlet temperature. Some cooling of the cooling air is also possible according to this embodiment at the outer limits of cooling air temperature, for example, when room temperature is substantially elevated from outside air temperature.
According to another embodiment of the present invention, when it is desired to be able to either heat or cool cooling air temperature to maintain a substantially constant cooling air temperature, a second indirect heat exchanger is employed and the second indirect heat exchanger is positioned downstream of the outlet from the cooling air blower. According to this embodiment, cold water from the inlet to the cooling water tower is delivered to the second indirect heat exchanger and, if and to the extent needed, the cold water from the outlet of the water cooling tower is throttled to ensure that the cooling effect of the water going to the second heat exchanger is proper for proper cooling of the cooling air stream. With proper automatic temperature control elements, when a pair of indirect heat exchangers are employed according to the second embodiment of the present invention, the temperature of the cooling air going to the molds of a glass manufacturing machine will remain substantially constant, notwithstanding wide variations in the temperature of the air entering the cooling air system, for example, normal day to night air temperature variations or seasonal air temperature variations.
Accordingly, it is an object of the present invention to provide an improved method and apparatus for controlling the temperature of cooling air going to the molds of a glass manufacturing machine. More particularly, it is the object of the present invention to provide a method and apparatus according to the foregoing character that is capable of controlling the temperature of cooling air employed in cooling the molds of a glass manufacturing machine at a substantially constant rate, notwithstanding wide variations of the temperature of the cooling air at the inlet to the cooling air system, for example, due to day to night or seasonal air temperature variations.
For a further understanding of the present invention and the objects thereof, attention is directed to the drawing and the following brief description thereof, to the detailed description of the invention and to the appended claims.